Anyone with an automatic and more than 1000 miles using 87 octane?

[xxxtreeboy]

What "real-world" mileage figures do you 87 octane users get with the auto tranny for mixed driving and highway lightly loaded as a daily commuter? Thanks

Please email me direct at wwpb@aol.com

Thanks, I appreciate it. Keep the rubber side down.

[jbreddawg]

Automatic just over 1100 miles. So far, first tank was around 14 mpg and I about had a heart attack !! But it only had 44 miles on it when I bought it. Milage has steadely increased with every tankful. Mind you, I am not easy on the throttle !!! I want to enjoy my truck, and do not drive like a grandma just to save a few "ok, maybe a few thousand" pennies !! The best I have seen so far is around 17 mpg. But like I said, it is getting better with every tankful !!
It is a 2 ton SUV afterall .

[treknwil]

I have about 1700miles on mine and I've been averaging around 18 to 19 mpg combo driving (city/highway ). Not to bad considering all the roof rack and lights I have on top .

[icebox]

1,600 miles on mine..1st tank 14.4...2nd tank 16.6...3rd tank..19.9,{ mostly highway}..so far though city/highway miles have been averaging around 18..i can live with that.

[Bostonian1976]

can someone explain why mileage gets better? Is the engine loosening up a bit?

[Kansas Law Dog]

1. Compression improves as the ring seat against the cylinder walls better during break-in - no blow-by.
2. Bearing tracks smooth as any roughness during manufacturer is worn away.
3. Timing chain loosens up (same reason as bearing improvement).
4. New Tire model flaws wear away.

The first is an engine efficiency improvement and the last three are reduction of friction.

[Bostonian1976]

Kansas Law Dog previously said:

1. Compression improves as the ring seat against the cylinder walls better during break-in - no blow-by.
2. Bearing tracks smooth as any roughness during manufacturer is worn away.
3. Timing chain loosens up (same reason as bearing improvement).
4. New Tire model flaws wear away.

The first is an engine efficiency improvement and the last three are reduction of friction.

so fuel is literally being blown out of the exhaust valves? no wonder we have black soot on our TRD exhausts

[nomowindo]

I seriously doubt there is virtually ANY actual improvement in gas for the first 10k miles and then perhaps 1 mpg.. What happens is, people drive a little more carefully, less agressively and want to "show" how much there gas mileage has "improved". Modern engines simply don't loosen up that much (unless you have a NASCAR engine) which already is very loose. I know some will disagree, but that is the real world.

[Kansas Law Dog]

Boston - the improvement in compression permits combustion gases to blow-by into the circulating oil and oil to be drawn into the combustion chamber on the intake stroke. The soot is from the oil drawn in during the intake stroke. It is then combusted and exhausted.

This is miniscule in proportion to the whole cycle, but a contributing factor to the soot. It decreases during break-in as the rings wear and seat better on the face of the cylinder wall.

[Freewheeling Frank]

nomowindo previously said:

I seriously doubt there is virtually ANY actual improvement in gas for the first 10k miles and then perhaps 1 mpg.. What happens is, people drive a little more carefully, less agressively and want to "show" how much there gas mileage has "improved". Modern engines simply don't loosen up that much (unless you have a NASCAR engine) which already is very loose. I know some will disagree, but that is the real world.

Uh, i will guess you are wrong. I am not an engineer or anything, and I agree people will ease up on their driving, but I think in the first 1k miles mileage can make some major improvements from the exact events Law Dog mentioned. There is a reason for a break in period.